[PATCH] clocksource: dw_apb_timer_of: support timer-based delay

Jisheng Zhang
2015-10-30T10:14:39Z

Dear Daniel,

On Fri, 30 Oct 2015 16:27:39 +0800
Jisheng Zhang <jszhang@marvell.com> wrote:

> Implement an ARM delay timer to be used for udelay(). This allows us to
> skip the delay loop calibration at boot on Marvell BG2, BG2Q, BG2CD
> platforms. And after this patch, udelay() will be unaffected by CPU
> frequency changes.

The commit msg doesn't follow "clocksource/drivers/...: Dnnn.."
But I guess I'll need to post v2, v3 ..., I'll change the msg style in v2.

Thanks,
Jisheng

>
> Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
> ---
> drivers/clocksource/Kconfig | 10 ++++++++++
> drivers/clocksource/dw_apb_timer_of.c | 16 ++++++++++++++++
> 2 files changed, 26 insertions(+)
>
> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> index a7726db..7b081805 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -29,6 +29,16 @@ config DW_APB_TIMER_OF
> select DW_APB_TIMER
> select CLKSRC_OF
>
> +config DW_APB_TIMER_BASED_DELAY
> + bool "DW APB timer based delay"
> + depends on ARM && DW_APB_TIMER_OF
> + default n
> + help
> + This option enables support for using the DW APB timer to
> + implement timer-based delay. It is useful for skiping the
> + delay loop calibration at boot on some platforms. And the
> + udelay() will be unaffected by CPU frequency changes.
> +
> config ROCKCHIP_TIMER
> bool
> select CLKSRC_OF
> diff --git a/drivers/clocksource/dw_apb_timer_of.c b/drivers/clocksource/dw_apb_timer_of.c
> index a19a3f6..4bab048 100644
> --- a/drivers/clocksource/dw_apb_timer_of.c
> +++ b/drivers/clocksource/dw_apb_timer_of.c
> @@ -16,6 +16,7 @@
> * You should have received a copy of the GNU General Public License
> * along with this program. If not, see <http://www.gnu.org/licenses/>.
> */
> +#include <linux/delay.h>
> #include <linux/dw_apb_timer.h>
> #include <linux/of.h>
> #include <linux/of_address.h>
> @@ -130,6 +131,17 @@ static void __init init_sched_clock(void)
> sched_clock_register(read_sched_clock, 32, sched_rate);
> }
>
> +#ifdef CONFIG_DW_APB_TIMER_BASED_DELAY
> +static unsigned long dw_apb_delay_timer_read(void)
> +{
> + return ~readl_relaxed(sched_io_base);
> +}
> +
> +static struct delay_timer dw_apb_delay_timer = {
> + .read_current_timer = dw_apb_delay_timer_read,
> +};
> +#endif
> +
> static int num_called;
> static void __init dw_apb_timer_init(struct device_node *timer)
> {
> @@ -142,6 +154,10 @@ static void __init dw_apb_timer_init(struct device_node *timer)
> pr_debug("%s: found clocksource timer\n", __func__);
> add_clocksource(timer);
> init_sched_clock();
> +#ifdef CONFIG_DW_APB_TIMER_BASED_DELAY
> + dw_apb_delay_timer.freq = sched_rate;
> + register_current_timer_delay(&dw_apb_delay_timer);
> +#endif
> break;
> default:
> break;